Etching method and etching apparatus

ABSTRACT

A mask material layer  102  of a desired pattern is formed on a silicon oxide film  101 . The exposed parts of the silicon oxide film  101  is etched in accordance with the pattern of the mask material layer  102  by plasma etching by using a mixed gas fed at a rate such that the ratio (C 5 F 8 +O 2 /Ar) of the total flow rate of C 5 F 8 +O 2  to the flow rate of Ar is 0.02 (2%) or less. Thus, a generally vertical right-angled portion is formed in the silicon oxide film  101 . Therefore, no microtrenches are formed, and etching into a desired pattern is precisely effected.

FIELD OF THE INVENTION

The present invention relates to an etching method and an etchingapparatus used for manufacturing a semiconductor device having a finecircuit structure or other devices having a fine structure; and, moreparticularly, to an etching method and an etching apparatus for etchinga silicon oxide according to a pattern of a mask material to formgrooves having an approximately right-angled portion and the like.

BACKGROUND OF THE INVENTION

Conventionally, in the semiconductor device manufacturing field, forexample, so-called dry etching for etching a desired portion by aneffect of a plasma produced from a certain etching gas has been widelyused to form a fine circuit structure of a semiconductor device.

Further, recently, also in other devices having a fine structure besidesa semiconductor device, their fine structures are manufactured byperforming dry etching for etching desired portions according to apattern shape of a mask, instead of a mechanical cutting and the like.

With regard to such dry etching, when silicon oxide is plasma-etched,for example, a gaseous mixture of gas containing carbon and fluorine,oxygen gas and inert gas is used. More specifically, for example, agaseous mixture which contains C₅F₈ gas, O₂ gas and Ar gas is used.

However, as a result of extensive researches conducted by the presentinventors, the following issue was identified in the aforementionedetching process. Namely, as shown in FIG. 6A, when a mask material layer102 with a desired pattern is formed on a silicon oxide film (e.g.,thermal oxide film) 101 which is on a semiconductor wafer W, thereafter,as shown in FIG. 6B exposed parts of the silicon oxide film 101 areplasma-etched according to the pattern shape of the mask material layer102 by using a gaseous mixture of C₅F₈ gas, O₂ gas and Ar gas to formgrooves (trenches) 103 on the silicon oxide film 101, as shown by thedotted lines, the issue is that undesirable grooves, i.e., so-calledmicrotrenches, are formed on the base portions of sidewalls (the angledportions of the grooves 103's bottom portions) where approximatelyright-angled portions should be formed.

Here, in order to numerically estimate the production of suchmicrotrenches, the etching depth of the silicon oxide film 101 of itsflat portion indicated by arrow A excluding the microtrench portion andthe etching depth of the silicon oxide film 101 of the microtrenchportion indicated by arrow B in FIG. 6B are measured, and then theirratio (B/A) (hereinafter, referred to as a microtrench coefficient) isobtained. Further, in an assessment using a microtrench coefficient, itis preferable that the microtrench coefficient is approximately 1, butin a case such as the example shown in FIG. 6B, as will be discussedlater, the value of the above-mentioned microtrench coefficient isgreater than or equal to 1.14.

If microtrenches as above are formed, for example when wiring materialsor other materials are buried in the grooves (trenches), it is possibleto have a problem such that the materials are not sufficiently buried inthe microtrench portions thereby forming a gap. Further, when being usedas a machine component and the like, it is possible to have a problemsuch that the component's mechanical strength is undermined because ofthe existence of microtrenches. Therefore, the formation ofmicrotrenches as above should be prevented as much as possible.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anetching method and an etching apparatus capable of preventing theformation of microtrenches and highly accurate etching to obtain adesired shape.

In accordance with one aspect of the invention, there is provided anetching method for etching a silicon-containing oxide according to apattern shape of a mask by using a gaseous mixture of gas containingcarbon and fluorine, oxygen gas and inert gas, wherein recesses areformed in the silicon-containing oxide by an etching carried out under acondition that a ratio of a total flow rate of the gas containing carbonand fluorine and the oxygen gas to a flow rate of the inert gas ((a flowrate of the gas containing carbon and fluorine+a flow rate of the oxygengas)/the flow rate of the inert gas) is smaller than or equal to 0.02,the recesses having approximately planar bottom portions formed of thesilicon-containing oxide and approximately vertical sidewall portionsformed of the silicon-containing oxide, and angled portions formed bythe sidewall portions and the bottom portions being substantially rightangled, and a formation of narrow groove shaped microtrenches issuppressed at the bottom portion sides of the angled portions.

Further, in the etching method of the present invention, the ratio ofthe total flow rate of the gas containing carbon and fluorine and theoxygen gas to the flow rate of the inert gas ((the flow rate of the gascontaining carbon and fluorine+the flow rate of the oxygen gas)/the flowrate of the inert gas) is smaller than or equal to 0.015.

Furthermore, in the etching method of the present invention, the ratioof the total flow rate of the gas containing carbon and fluorine and theoxygen gas to the flow rate of the inert gas ((the flow rate of the gascontaining carbon and fluorine+the flow rate of the oxygen gas)/the flowrate of the inert gas) is greater than or equal to 0.003.

Still further, in the etching method of the present invention, the inertgas is Ar.

Additionally, in the etching method of the present invention, the gascontaining carbon and fluorine is C₅F₈.

Moreover, in the etching method of the present invention, the etching isperformed by mounting an object to be processed having thesilicon-containing oxide on a lower electrode of an etching apparatus inwhich an upper electrode and the lower electrode are disposed to faceeach other and then applying a high frequency power to the lowerelectrode.

Further, in the etching method of the present invention, thesilicon-containing oxide is a silicon oxide film.

Furthermore, in the etching method of the present invention, the etchingis performed while a magnetic field is formed approximatelyperpendicularly to a high frequency electric field formed by the highfrequency power.

In accordance with another aspect of the invention, there is provided anetching method for etching a silicon-containing oxide according to apattern shape of a mask by using a gaseous mixture of gas containingcarbon and fluorine, oxygen gas and inert gas, the etching methodincluding, a first step of performing an etching by setting a ratio of atotal flow rate of the gas containing carbon and fluorine and the oxygengas to a flow rate of the inert gas ((a flow rate of the gas containingcarbon and fluorine+a flow rate of the oxygen gas)/a flow rate of theinert gas) as a first value; and a second step of performing an etchingby setting the ratio of the total flow rate of the gas containing carbonand fluorine and the oxygen gas to the flow rate of the inert gas ((theflow rate of the gas containing carbon and fluorine+the flow rate of theoxygen gas)/the flow rate of the inert gas) as a second value smallerthan the first value, wherein recesses are formed in thesilicon-containing oxide by an etching, the recesses havingapproximately planar bottom portions formed of the silicon-containingoxide and approximately vertical sidewall portions formed of thesilicon-containing oxide, and angled portions formed by the sidewallportions and the bottom portions being substantially right angled, and aformation of narrow groove shaped microtrenches is suppressed at thebottom portion sides of the angled portions.

Further, in the etching method of the present invention, the first valueis greater than 0.02 and the second value is smaller than or equal to0.02.

Furthermore, in the etching method of the present invention, the inertgas is Ar.

Still further, in the etching method of the present invention, the gascontaining carbon and fluorine is C₅F₈.

In accordance with still another aspect of the invention, there isprovided an etching apparatus for etching a silicon-containing oxideaccording to a pattern shape of a mask by using a gaseous mixture of gascontaining carbon and fluorine, oxygen gas and inert gas, whereinrecesses are formed in the silicon-containing oxide by performing anetching while supplying the gaseous mixture having a ratio of a totalflow rate of the gas containing carbon and fluorine and the oxygen gasto a flow rate of the inert gas ((a flow rate of the gas containingcarbon and fluorine+a flow rate of the oxygen gas)/the flow rate of theinert gas) smaller than or equal to 0.02, the recesses havingapproximately planar bottom portions formed of the silicon-containingoxide and approximately vertical sidewall portions formed of thesilicon-containing oxide, and angled portions formed by the sidewallportions and the bottom portions being substantially right angled, and aformation of narrow groove shaped microtrenches is suppressed at thebottom portion sides of the angled portions.

Further, in the etching apparatus of the present invention, the suppliedgaseous mixture has the ratio of the total flow rate of the gascontaining carbon and fluorine and the oxygen gas to the flow rate ofthe inert gas ((the flow rate of the gas containing carbon andfluorine+the flow rate of the oxygen gas)/the flow rate of the inertgas) smaller than or equal to 0.015.

Furthermore, in the etching apparatus of the present invention, thesupplied gaseous mixture has the ratio of the total flow rate of the gascontaining carbon and fluorine and the oxygen gas to the flow rate ofthe inert gas ((the flow rate of the gas containing carbon andfluorine+the flow rate of the oxygen gas)/the flow rate of the inertgas) greater than or equal to 0.003.

Still further, in the etching apparatus of the present invention, theinert gas is Ar.

Additionally, in the etching apparatus of the present invention, the gascontaining carbon and fluorine is C₅F₈.

Moreover, in the etching apparatus of the present invention, the etchingapparatus includes an upper electrode and a lower electrode disposed toface the upper electrode, wherein the etching is performed by mountingan object to be processed having the silicon-containing oxide on thelower electrode and then applying a high frequency power to the lowerelectrode.

Further, in the etching apparatus of the present invention, thesilicon-containing oxide material is a silicon oxide film.

Furthermore, the etching apparatus of the present invention includes amagnetic field forming mechanism for forming a magnetic fieldapproximately perpendicular to a high frequency electric field formed bythe high frequency power.

Moreover, a microtrench coefficient represented by a ratio of an etchingdepth of the silicon-containing oxide of the angled portions to anetching depth of the silicon-containing oxide other than the angledportions of the recesses is 1.10 to 1.00.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 2B are drawings that illustrate a preferred embodiment ofthe present invention's etching method;

FIG. 2 shows a schematic configuration of an etching apparatus inaccordance with the preferred embodiment of the present invention;

FIG. 3 are charts that illustrate the relations between (C₅F₈+O₂)/Ar andetching rate, and between (C₅F₈+O₂)/Ar and etching rate uniformity;

FIG. 4 is a chart that illustrates the relation between (C₅F₈+O₂)/Ar anda microtrench coefficient;

FIG. 5 provides the relations between (C₅F₈+O₂)/Ar and microtrenchcoefficient when the width of a trench is narrow; and

FIGS. 6A and 6B show drawings to illustrate the problem to be resolvedby the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will bedescribed in detail with reference to the accompanying drawings. FIG. 2schematically illustrates a configuration of an etching apparatus inaccordance with the preferred embodiment. Referring to FIG. 2, there isillustrated a cylindrical vacuum chamber 1 which makes up a plasmaprocessing chamber, wherein the chamber 1 is made of, for example,aluminum while its inner space is sealed airtight.

The vacuum chamber 1 is in stepped cylindrical form and is composed ofan upper part 1 a with a small diameter and a lower part 1 b with alarge diameter; the chamber is connected to a ground potential. Further,installed inside the vacuum chamber 1 is a supporting table (susceptor)2 to support a semiconductor wafer W as a substrate to be processed. Thetable supports the wafer W in such a manner that it lies in anapproximately horizontal position while its surface to be processedfaces upward.

The supporting table 2 is made of, for example, aluminum, and is held upby a conductive support 4 via an insulating plate 3 made of ceramic andthe like. Further, around the upper peripheral portion of the supportingtable 2, a focus ring 5 formed of conductive or insulating material isdisposed.

In addition, on the mounting surface of the supporting table 2 for thesemiconductor wafer W, an electrostatic chuck 6 is disposed toelectrostatically attract and hold the semiconductor wafer W. Theelectrostatic chuck 6 is formed of an insulator 6 b having an electrode6 a embedded therein, which is connected to a DC power supply 13. Then,by applying a voltage from the power supply 13 to the electrode 6 a, thesemiconductor wafer W is attracted and held on the chuck because of, forexample, a Coulomb force.

Moreover, installed within the supporting table 2 are a coolant channel(not shown) to circulate a coolant and a gas introduction mechanism (notshown) for supplying He gas to the bottom surface of the semiconductorwafer W to efficiently transfer cold heat from the coolant to thesemiconductor wafer W. Hence, it is possible to control thesemiconductor wafer W to a desired temperature. In addition, it isconfigured such that the pressure of He gas can be independentlycontrolled for the center portion and the edge portion of thesemiconductor wafer W. Further, with respect to the parts that make upthe inside processing space of the vacuum chamber 1, it is designed sothat the respective temperatures of their top, wall and bottom can beindependently controlled.

The supporting table 2 and the support 4 are elevated by a ball screwmechanism, which includes ball screws 7. The driving portion under thesupport 4 is covered with a bellows 8 made of stainless steel (SUS), andoutside the bellows 8, a bellows cover 9 is installed.

Further, a feeder line 12 for supplying a high frequency power isconnected to approximately the center of the supporting table 2. Amatching box 11 and a high frequency power supply 10 are connected tothe feeder line 12. A high frequency power ranging from 13.56 to 150 MHz(in this embodiment, a high frequency power of 13.56 MHz) is suppliedfrom the high frequency power supply 10 to the supporting table 2.

Further, a gas exhaust ring 14 is installed outside the focus ring 5.The gas exhaust ring 14 is electrically connected to the vacuum chamber1 through the support 4 and the bellows 8.

Meanwhile, at the ceiling portion of the vacuum chamber 1 above thesupporting table 2, a shower head 16 is installed so that it faces inparallel the supporting table 2 and the shower head 16 is grounded.Thus, it is designed so that the supporting table 2 and the shower head16 function as a pair of electrodes.

A plurality of gas discharge openings 18 are formed at the bottomsurface of the shower head 16, and a gas inlet 16 a is disposed at anupper portion thereof. Also, a gas diffusion space 17 is formed on theinside thereof. The gas inlet 16 a is connected to a gas supply line 15a, and at the other end of the gas supply line 15 a, a processing gassupply system 15 is connected in order to supply a processing gas foretching.

The processing gas for etching, which is supplied from the processinggas supply system 15, is a gaseous mixture, which contains gas of carbonand fluorine, oxygen gas and inert gas, while in this embodiment, it isa gaseous mixture which consists of C₅F₈ gas, O₂ gas and Ar gas. Theprocessing gas is supplied from the processing gas supply system 15 tothe gas diffusion space 17 of the shower head 16, through the gas supplyline 15 a and the gas inlet 16 a; then discharged through the gasdischarge openings 18, ultimately being supplied for etching a filmformed on the semiconductor wafer W.

Further, a gas exhaust port 19 is formed in the sidewall of the lowerpart 1 b of the vacuum chamber 1, and the gas exhaust port 19 isconnected to a gas exhaust system 20. In addition, by operating a vacuumpump installed in the gas exhaust system 20, the inner space of thevacuum chamber 1 can be decompressed to a certain vacuum level. Also,installed in the upper sidewall of the lower part 1 b of the vacuumchamber 1 is a gate valve 24 to open and close a loading/unloading portfor the semiconductor wafer W.

In the meantime, around the peripheral portion of the upper part 1 a ofthe vacuum chamber 1, concentrically with the vacuum chamber 1, aring-shaped magnetic field forming mechanism (ring magnet) 21 isdisposed, so that a magnetic field can be formed in a processing spacebetween the supporting table 2 and the shower head 16. The entiremagnetic field forming mechanism 21 can rotate around the vacuum chamber1 at a certain rotation speed by a rotation mechanism 25.

Also, as for the magnetic forming mechanism 21, it is possible to usethe type for forming a dipole magnetic field or one for forming amulti-pole magnetic field while in this embodiment, the magnetic fieldforming mechanism 21 for forming a dipole magnetic field approximatelyperpendicular to a high frequency electric field is used.

Further, an optical fiber 28 a is connected to a sidewall of a portioncorresponding to the processing space of the vacuum chamber 1, so thatcertain ultraviolet (UV) rays can be emitted from a UV light source unit28 to the processing space of the vacuum chamber 1 through the opticalfiber 28 a. UV rays are emitted to the processing space because it isdifficult to ignite a plasma only by applying a high frequency,depending on the resistance state in the vacuum chamber 1 (especiallythe electrode to which a high frequency is applied). Namely, by emittingUV rays and applying a high frequency simultaneously, the processing gascan be excited and ionized, thereby facilitating the plasma ignition.

Further, the shorter the wavelength of UV rays, the more preferable itis, and for example, smaller than or equal to 300 nm can be used. It ispreferable to emit the rays for, for example, 0.5 to 5 seconds. Inaddition, since the UV rays are introduced into the vacuum chamber 1 viathe optical fiber 28 a in this embodiment, ultraviolet rays with a shortwavelength smaller than or equal to 200 nm can be emitted without energyloss in the rays' introduction path. In case of a long wavelength, awindow is provided in the vacuum chamber 1 and then UV rays are emittedfrom the outside of the window into the vacuum chamber 1, therebyintroducing ultraviolet rays into the vacuum chamber 1.

Using an etching apparatus configured as described above, in thisembodiment, as illustrated in FIG. 1A, the semiconductor wafer W withthe mask material layer 102 having a desired pattern on the siliconoxide film (a thermal oxide film) 101 is used, and exposed parts of thesilicon oxide film 101 are etched according to the pattern shape of themask material layer 102, thereby forming the grooves (trenches) 103. Thegrooves (trenches) 103's width is about 5.75 μm.

The order of the etching is as follows: first, the gate valve 24 isopened, and the semiconductor wafer W is loaded into the vacuum chamber1 by a transfer mechanism (not shown) via a load-lock chamber (notshown) disposed adjacent to the gate valve 24. Thereafter, thesemiconductor wafer W is mounted on the supporting table 2, which hasbeen already lowered to a certain level. Then, by applying a certainvoltage from the DC power supply 13 to the electrode 6 a of theelectrostatic chuck 6, the semiconductor wafer W is attracted and heldby the Coulomb force.

Subsequently, after the transfer mechanism is withdrawn out of thevacuum chamber 1, the gate valve 24 is closed. Then, the supportingtable 2 is elevated to the level shown in FIG. 1 and, at the same time,the inside of the vacuum chamber 1 is exhausted through the gas exhaustport 19 by using the vacuum pump in the gas exhaust system 20.

After a certain vacuum level is achieved inside the vacuum chamber 1, aprocessing gas, which is a gaseous mixture of C₅F₈ gas, O₂ gas and Argas, is introduced at a certain flow rate from the processing gas supplysystem 15 into the vacuum chamber 1. The inside of the vacuum chamber 1is maintained at a certain pressure level such as at 1.33 to 133 Pa (10to 1000 mTorr); the pressure level is maintained at 13.3 Pa (100 mTorr)or 5.32 Pa (40 mTorr) in this embodiment.

Further, in such a state, a high frequency power with a certainfrequency, for example 13.56 MHz in this embodiment, is supplied fromthe high frequency power supply 10 to the supporting table 2 and, at thesame time, UV rays are emitted from the aforementioned UV light sourceunit 28 upon ignition of the plasma.

In this case, as a result of applying the high frequency power to thesupporting table 2 serving as a lower electrode, a high frequencyelectric field is formed in the processing space between the shower head16 serving as the upper electrode and the supporting table 2 as thelower electrode and, at the same time, a magnetic field is formed by themagnetic field forming mechanism 21. In that state, plasma etching ofthe silicon oxide film 101 is performed.

Further, once a certain etching process is carried out, supplying of thehigh frequency power from the high frequency power supply 10 is stoppedto terminate the etching process, and the semiconductor wafer W iscarried out of the vacuum chamber 1 in reverse order of theaforementioned sequence.

Here, more detailed etching conditions in the aforementioned etching aredescribed as follows:

-   -   C₅F₈/O₂/Ar=Jun. 4, 1000 sccm    -   ((C₅F₈+O₂)/Ar=0.01 (1%))    -   Pressure=13.3 Pa (100 mTorr)    -   High frequency output=1500 W    -   Gap between electrodes=27 mm    -   Backside He pressure (center/edge)=5320/26600 Pa (4/20 Torr)    -   Temperature (top/wall/bottom)=60/60/30° C.

Consequently, as illustrated in FIG. 1B, microtrenches are hardlyformed, and thus, it is possible to obtain approximately right-angledbase portions of the sidewalls. The microtrench coefficient (B/A) isabout 1.03 (A=4.84 μm, B=5.00 μm).

FIGS. 3 and 4 illustrate, with regard to the aforementioned etching ofthe silicon oxide film 101, changes in the etching rate (solid line C inFIG. 3), in the etching rate uniformity (in-surface uniformity) (a solidline D in FIG. 3) and in the microtrench coefficient (a solid line E inFIG. 4) when the ratio of the total flow rate of C₅F₈+O₂ to the flowrate of Ar ((C₅F₈+O₂)/Ar) is varied.

Further, in FIG. 3, the solid lines C and D are respectively broken intoP1 to P2 and P3 to P4 in the middle because the pressures are setdifferently at 13.3 Pa (100 mTorr) for the left solid line P1 to P2 andat 5.32 Pa (40 mTorr) for the right solid line P3 to P4 on the chart.

Further, specific flow rates of each gas in P1 as mentioned above are

-   -   C₅F₈/O₂/Ar=Jun. 4, 1000 sccm    -   ((C₅F₈+O₂)/Ar=0.01 (1%))    -   while P2 and P3 have the same flow rates as,    -   C₅F₈/O₂/Ar=Jun. 4, 19500 sccm    -   ((C₅F₈+O₂)/Ar=0.02 (2%)),    -   and P4 has,    -   C₅F₈/O₂/Ar=Dec. 9, 19500 sccm    -   ((C₅F₈+O₂)/Ar=0.04 (4%)).

Further, while with regard to P1, the microtrench coefficient (B/A) andspecific values of A and B are the same as the aforementioned values,the microtrench coefficient (B/A) of P2, P3 and P4 are about 1.10(A=5.43 μm, B=5.99 μm), 1.10 (A=5.87 μm, B=6.46 μm) and 1.15 (A=7.30 μm,B=8.37 μm), respectively.

As indicated by solid line E in FIG. 4, the microtrench coefficienttends to become more preferable as the ratio of the total flow rate ofC₅F₈+O₂ to the flow rate of Ar ((C₅F₈+O₂)/Ar) becomes smaller. It isrecommended that the microtrench coefficient ranges between 1.10 and1.00. Accordingly, the ratio of the total flow rate of C₅F₈+O₂ to theflow rate of Ar ((C₅F₈+O₂)/Ar) is preferably smaller than or equal to0.02 (2%) and, more preferably, smaller than or equal to 0.015 (1.5%).

On one hand, as illustrated by solid line C in FIG. 3, the etching ratetends to decrease as the ratio of the total flow rate of C₅F₈+O₂ to theflow rate of Ar ((C₅F₈+O₂)/Ar) gets smaller. Further, as displayed bysolid line D in FIG. 3, the etching rate uniformity (in-surfaceuniformity) also tends to deteriorate as the ratio becomes smaller.Therefore, the ratio of the total flow rate of C₅F₈+O₂ to the flow rateof Ar ((C₅F₈+O₂)/Ar) is preferably greater than or equal to about 0.003(0.3%).

Further, by changing the ratio of the total flow rate of C₅F₈+O₂ to theflow rate of Ar ((C₅F₈+O₂)/Ar) during an etching process, it is possibleto perform the etching process with multiple stages.

Namely, for example, in the initial stage of an etching process, inorder to increase its etching rate and to maintain a high in-surfaceuniformity of the etching rate, the ratio of the total flow rate ofC₅F₈+O₂ to the flow rate of Ar ((C₅F₈+O₂)/Ar) is set to a large value(e.g., greater than 0.02 (2%)).

Then, in the second stage of the etching process, to prevent theformation of microtrenches, the ratio of the total flow rate of C₅F₈+O₂to the flow rate of Ar ((C₅F₈+O₂)/Ar) is set to a small value (e.g.,smaller than or equal to 0.02 (2%)).

As described above, by changing the ratio of the total flow rate ofC₅F₈+O₂ to the flow rate of Ar ((C₅F₈+O₂)/Ar) during an etching processso that an etching process of multiple stages (e.g., two stages) isperformed and consequently, it is possible to prevent the formation ofmicrotrenches while increasing the etching rate and maintaining a highin-surface uniformity of the etching rate.

Further, a mechanism of suppressing the formation of microtrenches byselecting the gaseous mixture as described above is presumed to be asfollows. Namely, one of the causes for the formation of microtrenchesmay be due to a difference between the etching rate of the portionindicated by arrow A (flat portion of the grooves 103) and that of theportion indicated by arrow B (microtrench portion). The difference isattributed to an accumulation of a large amount of etching deposits thatslow down the etching rate in the flat portion. Further, as describedabove, when the ratio of the total flow rate of C₅F₈+O₂ to the flow rateof Ar ((C₅F₈+O₂)/Ar) is lowered and the amount of Ar in the gaseousmixture is increased, the above-mentioned deposits get removed by asputtering by Ar while the above-mentioned difference between theetching rates is reduced, thereby suppressing the formation ofmicrotrenches.

FIG. 5, unlike the case shown in FIGS. 1A and 1B, with respect toetching patterns with grooves (trenches) having a narrow width (e.g.,about 0.6 μm), illustrates the relations between the ratio of the totalflow rate of C₅F₈+O₂ to the flow rate of Ar ((C₅F₈+O₂)/Ar) and theetching rate (solid line F) and between the ratio ((C₅F₈+O₂)/Ar) and themicrotrench coefficient (solid line G).

Further, etching conditions with respect to flow rates are described asfollows, respectively:

-   -   C₅F₈/O₂/Ar=Jun. 4, 19500 sccm    -   ((C₅F₈+O₂)/Ar=0.02 (2%)) and    -   C₅F₈/O₂/Ar=Jun. 4, 19800 sccm    -   ((C₅F₈+O₂)/Ar=0.0125 (1.25%)).

Other conditions are described as follows:

-   -   Pressure=15.96 Pa (120 mTorr)    -   High frequency output=1400 W    -   Gap between electrodes=27 mm    -   Backside helium pressure (center/edge)=931/5320 Pa (7/40 Torr)    -   Temperature (top/wall/bottom)=60/60/20° C.

As illustrated in FIG. 5, even in a case where the width of grooves(trenches) is narrow, the ratio of the total flow rate of C₅F₈+O₂ to theflow rate of Ar ((C₅F₈+O₂)/Ar) is set smaller than or equal to 0.02(2%), so that the microtrench coefficient can have a preferred valuesmaller than or equal to 1.1.

Further, although the above embodiment describes a case where C₅F₈ isused as the gas containing carbon and fluorine, other gas species suchas C₄F₆, C₃F₈, and C₄F₈ can be used instead as a gas with carbon andfluorine.

Further, although this embodiment describes a case where Ar is used asthe inert gas, other inert gas species such as Xe and Kr can also beused.

Further, this embodiment describes a case where a thermal oxide filmformed on the semiconductor wafer W is etched as the silicon oxide to beetched, but the silicon oxide is not limited to the thermal oxide filmand can be CVD film, SOG film, quartz or the like, which may alsocontain impurities such as phosphorus and boron. Still further, it isnot limited to the silicon oxide on the semiconductor wafer W and can beapplied to every silicon oxide.

In addition, besides the silicon oxide film, this invention can beapplied to silicon-containing oxides known as inorganic low-K film suchas SiOC, SiON and SIOF.

Further, while an organic material such as resist is used as the maskmaterial, it may not function properly as a mask since the mask materialgets etched when the amount of etching is large. In such a case, aninorganic material film such as nitride film with a high etchingresistance, e.g., a silicon nitride film, can be used. Further, althoughthe etching apparatus used for etching is an apparatus in which a highfrequency voltage is applied to both an upper electrode and an lowerelectrode, it is possible to use other apparatuses such as ECR plasmaetching apparatus, helicon wave plasma etching apparatus, TCP plasmaetching apparatus, inductively coupled plasma etching apparatus and thelike.

As described above, in accordance with the present invention, theformation of microtrenches can be suppressed so that highly accurateetching of a desired shape can be performed.

While the invention has been shown and described with respect to thepreferred embodiments, it will be understood by those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

Industrial Applicability

An etching method and an etching apparatus in accordance with thepresent invention can be used in a semiconductor manufacturing industryfor manufacturing semiconductor devices and, therefore, have anindustrial applicability.

1. An etching method for etching a silicon-containing oxide according toa pattern shape of a mask by using a gaseous mixture of gas containingcarbon and fluorine, oxygen gas and inert gas, wherein recesses areformed in the silicon-containing oxide by an etching carried out under acondition that a ratio of a total flow rate of the gas containing carbonand fluorine and the oxygen gas to a flow rate of the inert gas ((a flowrate of the gas containing carbon and fluorine+a flow rate of the oxygengas)/a flow rate of the inert gas) is smaller than or equal to 0.02, therecesses having approximately planar bottom portions formed of thesilicon-containing oxide and approximately vertical sidewall portionsformed of the silicon-containing oxide, and angled portions formed bythe sidewall portions and the bottom portions being substantially rightangled, and a formation of narrow groove shaped microtrenches issuppressed at the bottom portion sides of the angled portions.
 2. Theetching method of claim 1, wherein the ratio of the total flow rate ofthe gas containing carbon and fluorine and the oxygen gas to the flowrate of the inert gas ((the flow rate of the gas containing carbon andfluorine+the flow rate of the oxygen gas)/the flow rate of the inertgas) is smaller than or equal to 0.015.
 3. The etching method of claim1, wherein the ratio of the total flow rate of the gas containing carbonand fluorine and the oxygen gas to the flow rate of the inert gas ((theflow rate of the gas containing carbon and fluorine+the flow rate of theoxygen gas)/the flow rate of the inert gas) is greater than or equal to0.003.
 4. The etching method of claim 1, wherein the inert gas is Ar. 5.The etching method of claim 4, wherein the gas containing carbon andfluorine is C₅F₈.
 6. The etching method of claim 1, wherein the etchingis performed by mounting an object to be processed having thesilicon-containing oxide on a lower electrode of an etching apparatus inwhich an upper electrode and the lower electrode are disposed to faceeach other and then applying a high frequency power to the lowerelectrode.
 7. The etching method of claim 6, wherein thesilicon-containing oxide is a silicon oxide film.
 8. The etching methodof claim 6, wherein the etching is performed while a magnetic field isformed approximately perpendicular to a high frequency electric fieldformed by the high frequency power.
 9. An etching method for etching asilicon-containing oxide according to a pattern shape of a mask by usinga gaseous mixture of gas containing carbon and fluorine, oxygen gas andinert gas, the etching method comprising: a first step of performing anetching by setting a ratio of a total flow rate of the gas containingcarbon and fluorine and the oxygen gas to a flow rate of the inert gas((a flow rate of the gas containing carbon and fluorine+a flow rate ofthe oxygen gas)/a flow rate of the inert gas) as a first value; and asecond step of performing an etching by setting the ratio of the totalflow rate of the gas containing carbon and fluorine and the oxygen gasto the flow rate of the inert gas ((the flow rate of the gas containingcarbon and fluorine+the flow rate of the oxygen gas)/the flow rate ofthe inert gas) as a second value smaller than the first value, whereinrecesses are formed in the silicon-containing oxide by an etching, therecesses having approximately planar bottom portions formed of thesilicon-containing oxide and approximately vertical sidewall portionsformed of the silicon-containing oxide, and angled portions formed bythe sidewall portions and the bottom portions being substantially rightangled, and a formation of narrow groove shaped microtrenches issuppressed at the bottom portion sides of the angled portions.
 10. Theetching method of claim 9, wherein the first value is greater than 0.02and the second value is smaller than or equal to 0.02.
 11. The etchingmethod of claim 9, wherein the inert gas is Ar.
 12. The etching methodof claim 9, wherein the gas containing carbon and fluorine is C₅F₈. 13.An etching apparatus for etching a silicon-containing oxide according toa pattern shape of a mask by using a gaseous mixture of gas containingcarbon and fluorine, oxygen gas and inert gas, wherein, recesses areformed in the silicon-containing oxide by performing an etching whilesupplying the gaseous mixture having a ratio of a total flow rate of thegas containing carbon and fluorine and the oxygen gas to a flow rate ofthe inert gas ((a flow rate of the gas containing carbon and fluorine+aflow rate of the oxygen gas)/a flow rate of the inert gas) smaller thanor equal to 0.02, the recesses having approximately planar bottomportions formed of the silicon-containing oxide and approximatelyvertical sidewall portions formed of the silicon-containing oxide, andangled portions formed by the sidewall portions and the bottom portionsbeing substantially right angled, and a formation of narrow grooveshaped microtrenches is suppressed at the bottom portion sides of theangled portions.
 14. The etching apparatus of claim 13, wherein thesupplied gaseous mixture has the ratio of the total flow rate of the gascontaining carbon and fluorine and the oxygen gas to the flow rate ofthe inert gas ((the flow rate of the gas containing carbon andfluorine+the flow rate of the oxygen gas)/the flow rate of the inertgas) smaller than or equal to 0.015.
 15. The etching apparatus of claim13, wherein the supplied gaseous mixture has the ratio of the total flowrate of the gas containing carbon and fluorine and the oxygen gas to theflow rate of the inert gas ((the flow rate of the gas containing carbonand fluorine+the flow rate of the oxygen gas)/the flow rate of the inertgas) greater than or equal to 0.003.
 16. The etching apparatus of claim13, wherein the inert gas is Ar.
 17. The etching apparatus of claim 16,wherein the gas containing carbon and fluorine is C₅F₈.
 18. The etchingapparatus of claim 13, comprising an upper electrode and a lowerelectrode disposed to face the upper electrode, wherein the etching isperformed by mounting an object to be processed having thesilicon-containing oxide on the lower electrode and then applying a highfrequency power to the lower electrode.
 19. The etching apparatus ofclaim 18, wherein the silicon-containing oxide is a silicon oxide film.20. The etching apparatus of claim 18, comprising a magnetic fieldforming mechanism for forming a magnetic field approximatelyperpendicular to a high frequency electric field formed by the highfrequency power.
 21. The etching method of claim 1, wherein amicrotrench coefficient represented by a ratio of an etching depth ofthe silicon-containing oxide of the angled portions to an etching depthof the silicon-containing oxide other than the angled portions of therecesses is 1.10 to 1.00.
 22. The etching method of claim 10, wherein amicrotrench coefficient represented by a ratio of an etching depth ofthe silicon-containing oxide of the angled portions to an etching depthof the silicon-containing oxide other than the angled portions of therecesses is 1.10 to 1.00.
 23. The etching method of claim 13, wherein amicrotrench coefficient represented by a ratio of an etching depth ofthe silicon-containing oxide of the angled portions to an etching depthof the silicon-containing oxide other than the angled portions of therecesses is 1.10 to 1.00.